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Embed cmd into sed replacement to have dynamic substitution

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# 1  
Old 10-02-2012
Embed cmd into sed replacement to have dynamic substitution
Hello,
Is it possible to embed the command output to the replacement of sed? Say I need to replace all the blank lines with random strings:
input:
Code:
ACCTTCGTCTTCTGG

GCTTGAGATGGTCCA

GCAGGGCTAGTGACG

GACGAGTCTCTTGAC

ACCAAATCAAAGATC

and output is:
Code:
>26aa36d934d44f06d15b3aab4645a602 $(date | md5sum)
ACCTTCGTCTTCTGG
>0b23ffccf2d708b8b3f0eaed1fbaeae7 
GCTTGAGATGGTCCA
>f7d0caf30e50bbf55f69678854b610cd
GCAGGGCTAGTGACG
>06a28f5fcc2e8c5d984cf2dd8bbd3a61
GACGAGTCTCTTGAC
>f47cd7fa172ab69142f76c6de7ea1c4f
ACCAAATCAAAGATC

something like:
Code:
sed 's/^$/'">$(date | md5sum)"'/g'

but above script print out single same string for each substitution, not as unique different string each time. i.e.
Code:
date | md5sum

is not dynamic. Any help? Thanks a lot!
Yifang
Last edited by yifangt; 10-02-2012 at 06:24 PM..
# 2  
Old 10-02-2012
Code:
while read l ; do [[ -z "$l" ]] && l=">`echo $RANDOM|md5sum|sed 's/ .*//'`"; echo "$l" ; done < infile

# 3  
Old 10-02-2012
RE
Worked like a chime!
The script is twisty to me. Could you explain the do part?
Code:
do [[ -z "$l" ]] && l=">`echo $RANDOM|md5sum|sed 's/ .*//'`";

Wait a minute, the replacement is not unique. Believe it is related to $RANDOM|md5sum. Any clue about this?
Thanks a lot!
Last edited by yifangt; 10-02-2012 at 07:59 PM.. Reason: update
# 4  
Old 10-02-2012
Code:
do [[ -z "$l" ]] && l=">`echo $RANDOM|md5sum|sed 's/ .*//'`";

if line ("$l") is empty replace with ">" plus random generated string (trailing space and other charachters removed).
# 5  
Old 10-03-2012
Explanation
Thanks! Now I understand the replacement part. Can I ask what this part does?
Code:
 [[ -z "$l" ]]

and How come you used && condition to check empty line. Still could not figure it out. Thanks again.
# 6  
Old 10-03-2012
&& : execute following statement if condition is true
This User Gave Thanks to rdrtx1 For This Post:
yifangt
# 7  
Old 10-03-2012
Quote:
Originally Posted by yifangt
Thanks! Now I understand the replacement part. Can I ask what this part does?
Code:
 [[ -z "$l" ]]

-z means "if string is zero length".
This User Gave Thanks to Corona688 For This Post:
yifangt
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